#include <fstream>
#include <vector>
#include <iostream>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m;
vector<int> graf[100005];
vector<int> grafT[100005];
int viz[100005];
int viz2[100005];
int timp = 1;
vector <int> nodOrd;
vector<int> componente[100005];

void dfs(int nod)
{
	for (int i = 0; i < graf[nod].size(); i++)
	{
		if (viz[graf[nod][i]] == 0)
		{
			viz[graf[nod][i]] = 1;
			dfs(graf[nod][i]);
		}
	}
	nodOrd.push_back(nod);
}

int nrComp = 0;

void dfs2(int nod)
{
	componente[nrComp].push_back(nod);
	for (int i = 0; i < grafT[nod].size(); i++)
	{
		if (viz2[grafT[nod][i]] == 0)
		{
			viz2[grafT[nod][i]] = 1;
			dfs2(grafT[nod][i]);
		}
	}
}

int main()
{
	fin >> n >> m;
	int x, y;
	for (int i = 0; i < m; i++)
	{
		fin >> x >> y;
		graf[x].push_back(y);
		grafT[y].push_back(x);
	}
	for (int i = 1; i <= n; i++)
	{
		if (viz[i] == 0)
		{
			viz[i] = 1;
			dfs(i);
		}
	}
	for (int i = nodOrd.size() - 1; i >= 0; i--)
	{
		if (viz2[nodOrd[i]] == 0)
		{
			nrComp++;
			viz2[nodOrd[i]] = 1;
			dfs2(nodOrd[i]);
		}
	}
	fout << nrComp << '\n';
	for (int i = 1; i <= nrComp; i++)
	{
		for (int j = 0; j < componente[i].size(); j++)
		{
			fout << componente[i][j] << ' ';
		}
		fout << '\n';
	}
}